What a great question,
Do the defenders get rewarded for preventing a grounding and return-shoving the maul ( that supposedly ended, but still appeared to physically exist) by getting the feed at the scrum5?
Or
Does the theoretical "maul ending succesfully" (of L17.5) ...
[despite it kinda continuing in reality] retain the attackers the feed at the scrum5, & what would happen if the defensive effort pushed this ' already ended earlier' maul back up to say 15m from the goal line ....what would you do then ???? Say it ended back in the goal area and walk back to set a scrum 5? That would look awful.
On balance I don't think L17.5 (part 3) intended to deal with the HokeyCokeyMaul, so I'd say the defence should get the reward for their maul shove efforts.
So, for me, taken into maul by Red =
* if deemed unplayable whilst within the Goal area - scrum 5 red
* if deemed unplayable after it was shoved back out - scrum 5 blue ( or at 6m/7/8/9...15m ceased moving point )
Personally , watching a choke tackle metamorph into a 'uncollapsed' maul & then receive 'hokeycokey goal line shoving' would be an enjoyable watch .......until it remained static for 5 seconds after UI was announced , now I'm bored - so let's scrum